The US company has announced that the first patient has been dosed in a Phase II clinical trial of Dimebon (dimebolin), a drug that has been used in Russia since the 80s as an antihistamine but has also now been shown to be effective at protecting brain cells.

Huntington's disease is a progressive, neurodegenerative disease that affects 30,000 patients in the U.S., with another 150,000 at risk. It is caused by the death of specific brain cells and is characterized by the gradual development of involuntary muscle movements, progressive deterioration of cognitive processes and memory (dementia), and severe behavioral disturbances. There are no drugs approved by the FDA to treat this uniformly fatal genetic disorder.

The drug has already completed a Phase II trial in Alzheimer's patients, where investigators saw significant improvement over placebo on all five clinical endpoints at 6 months, including cognition and memory, activities of daily living, overall function, and behaviour.

Medivation is now looking to test its theory that Dimebon could also be effective at treating Huntington's disease. The drug is thought to block a new target that involves mitochondrial pores, which are believed to play a role in the cell death that is associated with neurodegenerative diseases and the aging process.

It is also believed to block both cholinesterase and the NMDA receptor simultaneously. Of the five existing FDA-approved drugs for Alzheimer's disease, all of them target one of these receptors, although none is thought to effect both, unlike Dimebon.

The Huntington's trial has enrolled 90 patients - up 20 per cent from the originally planned number - and will test the drug over three months. The primary endpoint is the Unified Huntington's Disease Rating Scale (UHDRS), with the company expecting to report results in the first half of next year.

"We are pleased that the results from the Phase 1 portion of our Huntington's disease study allow us to move forward to the preliminary efficacy phase," said David Hung, CEO of Medivation.

"Given the robust efficacy and safety results Dimebon achieved in our recently completed Alzheimer's disease trial, we are excited about Dimebon's potential to benefit Huntington's disease patients."

Meanwhile, Intellect Neurosciences has announced Phase Ia results for its lead drug candidate Oxigon, which is being tested as an Alzheimer's disease therapy. It was the first time humans had been exposed to pharmacological doses of the drug, according to Dr Daniel Chain, Intellect's CEO. The results of the trial showed no serious adverse effects in any of the subjects throughout the dose levels.

"The drug acts through unique modes of action that appear to target primary steps in a neurodegenerative molecular cascade that leads ultimately to learning and memory deficits in Alzheimer's patients," said Dr Paul Bendheim, chairman of Intellect's clinical advisory board.

The drug could also potentially be used to treat other neurodegenerative disorders such as Huntington's and Parkinson's disease. The compound itself is a synthetic version of a small, naturally occurring molecule that the company claims has unique anti-fibrillogenic, neuroprotectant and antioxidant properties.

It is hoped that Oxigon will reduce the accumulation of toxic soluble beta-amyloid peptides and inhibit plaque formation, which are thought to cause the debilitating effects of Alzheimer's. It also acts as a neuroprotectant, preventing neuronal damage from beta-amyloid-induced oxidative stress.